In recent years, field of utilizing dyes or dyestuffs having intense fluorescent property has been rapidly broadened. For example, fluorescent dyes or dye-stuffs have shown more variety in application, such as not only in dyeing or printing various synthetic fiber materials, dope coloring of various synthetic resins, melt spinning-dyeing, as fluorescent pigments in fluorescent dyes or inks, etc. but also in colored laser beams, solar batteries as a convergent system, display devices, and the like.
The present inventors have previously found that the following compounds A and B are fluorescent dyes having excellent fastness to light: ##STR2##
However, these compounds involve a problem in practical use from the standpoint of affinity for organic substrates. In some detail, when they are used as disperse dyes for dyeing polyester cloth, they were of low practical use due to their poor build-up property and temperature dependence. Further, when they are used as fluorescent pigments in combination with resin components, such as toluenesulfonamide, formaldehyde, melamine, etc., the compatibility with these resin components is poor, resulting in low fluorescent intensity and fastness to light when being spread on a paper substrate, etc.